Joint for artificial limb



Nov. 19, 1963 J. w. BAcH 3,110,906

JOINT FOR ARTIFICIAL LIMB Filed July 5, 1961 Johann W. Bach INVENTOR.

AGENT.

United States Patent 3,110,906 JOINT FOR ARTIFICIAL LlMB Johann W. Bach,Germaniaplatz 267, Essen-Borbeck, Germany Filed July 3, 1961, Ser. No.121,564 Claims priority, application Germany Nov. 30, 1960 a 6 Claims.(Cl. 3-27) My present invention relates to prosthetic limbs and moreparticularly to a physical joint, such as a knee joint, for such limbs.

It is an object of my invention present to provide a prosthetic limbwith a physiological joint which kinematically and cosmetically, i.e.,both in the relatively mobility of the parts and in its outerappearance, closely approximates the corresponding joint of a naturallimb.

It is another object of the present invention to provide an artificiallimb which is long-wearing and requires practically no adjustment evenafter protracted use.

A further object of this invention is the provision of improved means inan artificial limb adapted to prevent buckling at a joint substantiallyin the manner of a natural knee cap.

Another object of the present invention is to provide a jointedartificial limb of simple design, low weight and aesthetic appearanceadapted to be used as an exposed appliance on, for example, a bathingbeach.

In accordance with this invention I provide a joint for hingedlyinterconnecting two members of a prosthetic appliance, such as a thighportion and a shank portion, which resembles an anatomical knee jointand includes a knuckle-shaped termination on one (usually the upper)member co-operating with a complementary socketshaped termination on theother member. The two terminations have substantially cylindricalrolling surfaces of dilferent radii for relative swinging and slidingmovement, the knuckle being provided with a hinge pin or shaft whichextends in the direction of its cylinder axis (e.g., is in line with it)and is so disposed that in standing position this shaft lies rearwardlyof the center of gravity of the load supported by the appliance wherebythe body weight of the wearer tends to cause a forward swing of theartificial thigh from its substantial alignment with the artificialshank. One or more flexible straps, e.g., of steel or nylon, areanchored to the socket and looped around the shaft in correspondingrecesses of the knuckle so as to facilitate relative bending of themembers; to prevent the aforementioned forward swing beyond the erectposition, suitable anti-buckling means may be provided, advantageouslyin the shape of one or more abutments on the knuckle bearing upon theretaining strap or straps from the front to limit the extent of relativerotation of the members. The retaining straps, which in a preferredembodiment have the shape of V-belts, may be provided with meansaccessible through a suitable window in the socket-forming member foradjusting their tension, e.g., for the purpose of compensating forcreeping elongation thereof.

The main advantages of prosthetic limbs with physiological knee jointsaccording to my invention are their relatively constant kinematicalproperties, their very good cosmetic qualities, a relative simpledesign, and their possibility of being made entirely from non-metallicparts with consequent decrease in weight.

These and other objects, features and advantages of my present inventionwill become more clearly apparent from the following description of apreferred embodiment of the invention, given in conjunction with theaccompanying drawing in which! FIG. 1 is a section side view of aprosthetic limb according to the present invention;

, 3,110,906 Patented Nov. 19, v19,63

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FIG. 2 is a front view of the limb shown in FIG. 1;

FIG. 3 is a rear view of the same;

FIG. 4 is a sectional view of the limb taken along line IV-IV of FIG. 1;and

FIG. 5 is a side view of the prosthetic limb in a bent position.

The artificial limb shown in the drawing comprises a thigh member 2 anda hollow shank member 1 connected by a knee joint 12. The lower par-t ofthe thigh portion 2 ends in a knuckle 4 having a substantiallycylindrical rolling surface with a portion 5 of transitional curvature.The knuckle 4 is divided by two recesses 13a, 13b into three protrudingsections 4a, 4b, 40 whose outer areas form a cylindrical rollingsurface. These sections are supported by respective antif riction strips14a, 14b, 140, preferably made of plastic (e.g., a polyacrylate orpolytetrafiuoromethane), on the upper part of the shank 1 which ends ina socket 3 co-operating with the knuckle 4 to form the joint 12. Thesocket 3 is provided with two projecting portions 3a, 3b which enter therecesses 13a, 16b between the cylindrical socket portions 4a, 4b, 4c;these portions have a radius somewhat smaller than that of the concaveupper surface of socket 3 on which they are cradled and to which theantifriction strips 14a, 14b, are fastened by screws 17.

A shaft 7 passes through the knuckle portions 4a, 4b, 40 approximatelyalong the geometrical axis of their cylindrical rolling surface. Twoparallel V-bel-t straps 8a, 8b are anchored to the socket 3 within thecavity of the hollow shank 1 and are respectively accommodated by therecesses 13a, 13b within which they are looped around the shaft 7. Thestraps 8a, 8b pass through socket 3 via two openings 18' near the shinside and two openings 18" near the calf side of the shank 1 and areanchored at their front ends by cotter pins 11' bearing upon the upperwall 6 of the shank cavity. The rear extremities of the straps 8' areadjustably fastened by cotter pins 11' which bear upon one or moregaskets 15. An elastic block 10 is interposed between the gaskets 15 andthe wall 6. The tension in the straps 8 may be increased by addingfurther gaskets .15 through a window 16 which is conveniently providedin the upper calf section of the shank 1 to give access to its interior.Stops 9 in the front sections of the recesses 13a, 13b abut the V-belts8a, 8b in the straightened portion of the jointed limb to limit theforward swing of thigh 2 about shaft 7.

The operation of the prosthetic limb joint according to my presentinvention may be best described with reference to FIGS. 1 and 5. In thebent state illustrated in FIG. 5 the thigh member 2 and the shank member1, held together at the joint 12 by the straps 8a, 8b, occupy a relativeposition in which shaft 7 lies somewhat forwardly of the vertical radialplane of the rolling surface of socket 3, owing to the weightdistribution of the lower member 1 which is suspended [from the joint 12by the straps 8a, 8b in the seated position of the amputee. As the legis straightened, the center of rotation of the knuckle 4 as representedby the shaft 7 slides slightly toward the rear as the body weight of thewearer shifts the erect thigh 1 from the dot-and-dash position of FIG. 1to the rsolid-line position thereof. Now the stops 9 bear upon thestraps 8a, 8b and through themupon the ridges 3a, 3b of the socket 3,thereby limiting the forward swing of the thigh 2 which together withthe body weight supported by it has a center of gravity located in thisposition forwardly of the shaft 7, i.e., to the left of it as viewed inFIG. 1. The joint is therefore locked against buckling in this positionand remains so until the Weight of the wearer is transferred to theother leg. The kinematics of the artificial joint 12 therefore followclosely those of a natural knee joint.

Various modifications may suggest themselves to those skilled in the artand may be adopted without departing from the spirit and scope of myinvention and, hence, I do not wish to be restricted to the detailsshown and described, except to the extent indicated in the appendedclaims.

I claim:

1. A prosthetic limb comprising a thigh member and a shank memberinterconnected by a lcnee joint, said thigh member being provided with asubstantially cylindrical knuckle portion forming part of said joint,said shank member having a substantially cylindrical-1y concave bearingsurface receiving said knuckle portion for rolling displacement thereon,a shaft on said knuckle portion extending in the direction of thecylinder axis (thereof, and flexible link means yieldably embracingstaid shaft and projecting from said bearing surface, said shaft beingpositioned rearwardly of the center of gravity of the thigh-supportedload in an erect position of the wearer, ,said bearing surface having acylinder radius slightly greater than that of said knuckle portion forenabling the latter to roll forwardly in said erect position, furthercomprising anti-buckling means on one of said members for limiting theforward rolling of said knuckle portion.

2. A prosthetic limb according to claim 1 wherein said anti-bucklingmeans comprises an abutment on said knuckle portion engageable with saidlink means in said limiting position.

3. A prosthetic lim b according to claim 1 wherein said knuckle portionis provided with a plurality "of recesses axially dividing it intosections, said link means comprising a plurality of straps respectivelylooped in said recesses about said shaft.

4. A prosthetic limb according to claim 3 wherein said surface isprovided with a plurality of upstanding ridges respectively enteringsaid recesses: for centering said knuckle portion thereon.

5' A prosthetic limb according to claim 3 wherein said straps are V-belts.

6. A prosthetic limb according to claim 3 wherein said bearing surfaceis provided a plurality of anti-friction strips respectively supportingsaid sections.

References Cited in the file of this patent FOREIGN PATENTS

1. A PROSTHETIC LIMB COMPRISING A THIGH MEMBER AND A SHANK MEMBERINTERCONNECTED BY A KNEE JOINT, SAID THIGH MEMBER BEING PROVIDED WITH ASUBSTANTIALLY CYLINDRICAL KNUCKLE PORTION FORMING PART OF SAID JOINT,SAID SHANK MEMBER HAVING A SUBSTANTIALLY CYLINDRICALLY CONCAVE BEARINGSURFACE RECEIVING SAID KNUCKLE PORTION FOR ROLLING DISPLACEMENT THEREON,A SHAFT ON SAID KNUCKLE PORTION EXTENDING IN THE DIRECTION OF THECYLINDER AXIS THEREOF, AND FLEXIBLE LINK MEANS YIELDABLY EMBRACING SAIDSHAFT AND PROJECTING FROM SAID BEARING SURFACE, SAID SHAFT